Production of methylchlorosilanes



Patented Dec. 5, 1950 UNITED STATES PATENT Kenmore, N.

Y., assignors to The Linde Mr Products Company, a corporation of illiioNo Drawing.

Application September 13, 1909, Serial No. 115,546

2 Claims. (Cl. 2604483) The invention is a process for makingmethylchiorosilanes, particularly CHaSlCia and (CH3) :SIClzEthyltrichlorosilane can be prepared in several ways, the methoddescribed in application Serial No. 702,084, filed October 9, 1946, byGeorge H. Wagner and Corneiile 0. Strother being especiallyadvantageous. The nature of that method is indicated by the equation Wehave now found that methylchlorosilanes can be readily produced byhydrogenating ethyltrichlorosilane in the presence of a boron halidecatalyst such as BC]; or BFs.

The hydrogenation can be carried out as a continuous process, but theexperimental work on which this description is based was batch-wiseprocedure. Approximately equimolar proportions of CzHsSlCIa andhydrogen, together with the catalyst, were sealed in a stainless steelreactor, which was then heated. The reactor was cooled, and its contentsfractionated.

Reaction did not occur to a measurable degree in the absence of acatalyst. The recommended quantity oi the latter, under the conditionscited above, is 2 cc. of B01: per moi of C-iII-sSiCla; but one-half thisquantity of catalyst gave nearly as good results, and doubtless stillless would be effective, although possibly necessitatingprolongation ofthe heating time.

The lower limit of the favorable temperature range is just above 400 C.Results at 425 C. were much better than at 400 0., but raising thetemperature to 450 (3. gave little additional improvement.

When the relation of quantity of CaIIsBlCla to volume oi reaction spacewas 1.7 mole per liter. the pressure which developed at'450 C. was2200p. s. 1., and reaction did not occur. Pressures above 2500 p. s. i. arerecommended. When the quantity of CsHsSlCl: per liter of reaction spacewas double that cited above. the pressure developed was greater than5000 p. s. l. (the maximum which could be registered on the onlyavailable gauges adapted to be connected to the apparatus used) but wasestimated to be less than 10.000 p. s. i. We regard this as the optimumpressure range.

A reaction time of two hours gave a considerably more complete reactionthan did one hour. and longer times moderately increased the yield ofmethylchlorosilanes.

In a typical run, 3.3 mols each of CiHtSiClQ and H: per liter ofreaction space were used, with 2 cc. of 13013 per mol of CaHsSiC'h. Thetemperature was 450' 0., the time 14 hours, and the pressure developedwas more than 5000 p. s. i. The product recovered was 82% by weight ofthe C2HsSiCla taken, and contained 7 Per cent HSiCla+HrSiCiz 2 10CHsSlCls-l-(CHshSlCls 47 $1014 21 C2HsSiCla (unreacted) 12 (CfilHSiC'l:2 Residue on distillation 17 About 10% of this fraction was (cmhsicn.

Throughout the experimental work it was ob-- served that the S1014formed increased in rough proportion to thedesired methylchlorosilanes.Following this clue, it was found that the yields 20 ofmethylchlorosilanes could be significantly im- R-CaHi-SlCl:

where R is hydrogen or trichlorosilyl, said reaction occurring in thepresence 01' a boron halide at a temperature above 400 C. and at apressure v above 2500 p. s. i.

2. Process according to claim 1 where R in the type formula is hydrogen,the temperature is about 450 0., and the pressure is at least 5000 p. s.l.

DONALD L. BAILEY.

GEORGE H. WAGNER.

REFERENCES CITED file of this patent UNITED STATES PATENTS Number NameDate.

2.400.605 Hurd Aug. :27, 1945 2,458,703 Hatcher Jan. 11, 1949 Thefollowing references are of record in the

1. PROCESS FOR MAKING METHYLCHLOROSILANES WHICH COMPRISES REACTINGHYDROGEN WITH A COMPOUND OF THE TYPE R-C2H4-SIC13 WHERE R IS HYDROGEN ORTRICHLOROSILYL, SAID REACTION OCCURRING IN THE PRESENCE OF A BORONHALIDE AT A TEMPERATURE ABOVE 400*C. AND AT A PRESSURE ABOVE 2500 P. S.I.